This invention relates to a shed-forming device for a weaving machine, comprising a number of combinations of at least two selection systems respectively with selection elements provided one above the other whereby each selection system comprises two hooks working together and that can be moved up and down by lifting means, which can be selected by a selection element so that they are held at a fixed height.
This invention more especially relates to an electronically controlled jacquard machine, in particular a two-position and a three-position open-shed jacquard machine, which is provided with selection systems with the above mentioned characteristics.
This invention finally also relates to a weaving machine provided with such a shed-forming device or jacquard machine.
Jacquard machines with selection systems are of course very well known. In the European patent publication EP 0 188 074 for example a selection and guiding device for the hooks of an electronically controlled two-position open-shed jacquard machine is described. The selection element is an electromagnet. The hooks are flexible and made out of ferromagnetic material. The electromagnet can bend the hooks to a first position whereby the hook is engaged by an up-and-down-moving knife, and to a second position whereby the hook hooks onto a projection (is selected) and is therefore held at a fixed height.
In this manner a hook can be allowed to move up and down at will or held at a fixed height.
It is generally known how in this manner the position of two hooks working together is determined and the warp yarns on a weaving machine can be brought by means of pulley cords and pulley elements, to two different heights according to the open-shed principle. It is furthermore also known how by means of two selection systems working together each with a pair of hooks and pulley elements working together three different positions can be achieved.
Furthermore from the Belgian patent no. 1 009 047 a three-position open-shed jacquard machine is known, of which each selection system comprises two electromagnetic coils placed one above the other. These coils are provided in order to act on two hooks working together that are implemented in two parts. The hooks can be moved up and down by two knife systems operating one above the other. This device can only operate as a three-position open-shed jacquard machine.
An important characteristic of a shed-forming device is the so-called footprint of each selection system, or in other words the surface area that one selection system occupies on a perpendicular projection of the device onto a horizontal plane.
The footprint is also the product of the pitch in the width and the pitch in the depth of the device, whereby xe2x80x9cthe pitchxe2x80x9d is the width or the depth (in mm) of the area occupied by one selection system.
The above mentioned known jacquard machines can be implemented with a footprint of 8xc3x9722 mm2. This is rather large. Because of this the number of selection systems per machine is limited and the dimensions of the machine become too large if the number of selection systems is increased.
A purpose of this invention is to remedy these disadvantages by providing a shed-forming device with a considerably smaller footprint, with which the number of selection systems per surface area unit can therefore be increased, and whereby the device can be implemented as desired in order to bring warp yarns into two positions or three positions.
From the European patent publication EP-0851048 a shed-forming device is known with combinations of two selection systems with selection elements provided one above the other, with which the number of selection systems per surface area unit can be increased.
This device however has a number of significant disadvantages. Each combination comprises two hook pairs of which the hooks belong to different selection systems of that combination. The hooks of each hook pair rest on one another and are lying against each other during their up- and downwards movements. For the selection of one hook of two hooks fitting against each other the respective selection elements must be provided with (through an electromagnet) positionable holding means that hook into a selection position in an opening of a hook. These selection elements must furthermore ensure a very accurate positioning of the holding means.
These selection means are consequently rather complex and expensive. An additional purpose of this invention is also to remedy this disadvantage.
The above mentioned aims are achieved with a shed-forming device that has the characteristics that are mentioned in the first paragraph of this specification, whereby the hooks of the various selection systems of a combination can be moved up and down separately from each other.
With such a shed-forming device two or more selection systems can be provided within almost the same footprint surface area as one selection system according to the state-of-the-art. If according to this invention for example two selection systems are provided per combination the footprint will be almost halved and the number of selection systems with similar machine dimensions will be almost doubled in relation to the known devices.
The device according to this invention can comprise shed-forming systems with which warp yarns can be brought into two different positions, but can also be so implemented that per combination two selection systems work together with each other in order to bring warp yarns into three different positions.
Since the hooks of different selection systems here can be moved completely independently and separately from each other they can also easily each be selected individually by means of a selection element that does not have to be able to position any holding means with great precision in order to operate efficiently. Such a selection element can therefore be made rather simple, and therefore inexpensively.
A purpose of this invention was to increase the number of selection systems per surface area unit. Each arrangement of selection elements at levels located one above the other that leads to that end corresponds to the invention idea. The significance of the expression xe2x80x9cdisposed one above the otherxe2x80x9d in this specification and in the claims attached hereto may therefore certainly not be interpreted as a restriction on the invention to selection elements disposed one above the other of which the vertical planes of symmetry almost converge or lie close to each other.
For a correct interpretation of this specification and of the claims attached hereto two selection elements must be considered as being xe2x80x9cdisposed one above the otherxe2x80x9d if they are disposed at a different height and if the vertical projections onto a horizontal plane of these selection elements at least partially overlap each other or lie next to each other with an intermediate distance that is smaller than the minimum intermediate distance between neighboring selection elements of a shed-forming device according state-of-the-art.
The shed-forming device according to this invention is preferably so implemented that the hooks of selection systems of a same combination are movable by one and the same pair of lifting means, and that each lifting means comprises at least two parts for engaging a respective hook of a different selection system of the same combination.
Thus for a same number of selection systems only half the number of lifting means are necessary in comparison to the known devices, while the hooks can be engaged well separated from one another by a same lifting means.
Preferably the aforesaid parts of each lifting means are provided at least at two different levels. The hooks of a same combination that can be engaged by a same lifting means can because of this be moved up and down still better separated from each other, and therefore without hindering each other.
According to a particular embodiment of this invention each lifting means comprises a passage through which hooks can traverse the lifting means.
Of the hooks of a same combination that can be engaged by a same lifting means one hook can extend downward from its top extremity through this passage to below the lifting means. This hook therefore has a part above the lifting means that is for example provided with means for being held at a fixed height when selected by a selection element and when not selected for resting on an engagement means of the lifting means, and a part below the lifting means that is provided, for example via pulley cords and pulley elements, for influencing the position of one or several warp yarns on a weaving machine.
The hooks that extend through the passage are guided herein during the course of their up- and downwards movements, and separated from the other hooks on the same lifting means.
In a particularly advantageous embodiment the device comprises at least one row of several combinations of two selection systems disposed next to each other, and the top and the bottom selection elements are disposed mutually shifted according to the direction of the row. With such a disposition the hooks selected by these selection elements are also disposed shifted and two shifted disposed hooks can be used for the two hooks working together of each selection system so that the pulley elements working together with these hooks occupy a position whereby their operating planes are oblique in relation to the direction of the aforesaid row.
Two pulley elements of a same combination can also be provided next to each other, with almost parallel operating planes, through a suitable selection of the hooks working together therewith or two pulleys can be brought into a position whereby their operating planes intersect each other.
According to a preferred embodiment each combination comprises a top and a bottom selection element with two opposite selection flanks for the selection of respective hooks, and the selection flanks of the bottom selection element lie closer together than the selection flanks of the top selection element.
A number of selection systems can be provided in order to bring warp yarns into two different positions and/or a number of sets of two selection systems (preferably selection systems that belong to the same combination) can be provided in order to work together in order to bring warp yarns into three different positions.
Each combination in a most preferred embodiment of this invention comprises two selection systems with a respective pair of hooks working together, whereby these hooks can be engaged by two lifting means capable of moving up and down in opposite phase, and whereby each lifting means comprises a top and a bottom engagement means for engaging a respective hook of a different pair of hooks working together of a same combination.
It is furthermore also preferred that the device is so implemented that it comprises at least one row of several combinations of two selection systems disposed next to each other, whereby the lifting means working together with these selection systems are provided in order to engage hooks of two combinations disposed next to each other. In this manner the device is constructed with a minimum number of lifting means.
According to a particular embodiment the device comprises at least one row of several combinations of selection systems disposed next to each other, of which each shed-forming system comprises at least one pulley element working together with the hooks, while the pulley elements of the selection systems that belong to a same combination are suspended next to each other or one below the other, and while the operating planes of the pulleys of these pulley elements are mutually almost parallel and are either transverse to the direction of the row or are oblique in relation to this direction.
The device furthermore preferably also comprises at least one row of several combinations of selection systems disposed next to each other, of which each selection system comprises at least one pulley element working together with the hooks, so that the operating planes of at least two pulleys that belong to a same combination intersect each other.
In the following detailed specification of an embodiment example of this invention the aforesaid characteristics and advantages of the invention are further explained and the additional properties and advantages thereof are indicated. The purpose of this specification is only to give a clarifying example of a number of possible embodiments according to this invention and can therefore in no way be interpreted as a restriction on the range of application of the invention or on the patent rights claimed in the claims.